Observation: My Father Got Temporary Hyperacusis After Getting Hearing Aids

My father has severe hearing loss and finally decided to get hearing aids a few months back. The audiologist told him that in the first few weeks/days, many things will sound painful because his brain is not used to processing noise that loud anymore. He also claimed that his brain would adapt to this.

My father then finally understood what I'm going through with my hyperacusis. As predicted, his brain habituated to his hearing aids.

What is the difference with hyperacusis and tonic tensor tympani syndrome? Why don't our brains habituate to everyday sounds like my father's did?